On Thu, 13 Dec 2007, Ow Mun Heng wrote:
> I'm using centos 5 as the OS so, there's no fancy dtrace to look at
> which processes is causing my disks to thrash.
Does plain old top show you anything interesting? If you hit 'c' after
starting it you'll get more information about the postgres processes in
particular.
> 1 OS disk [hda]
> rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
> hda 98.60 14.69 121.98 15.08 1775.02 2908.29 34.17 47.53 551.67 7.29 99.95
The funny thing here is that both the writes and reads are very high
compared to the other disks. That rules out most of what I go looking for
when there's run-away activity. Many common causes do almost all reads
(i.e. some filesystem crawler like updatedb running) or almost all writes
(loggers gone wild!). Swapping might do both, so consider mine a second
vote to correlate this with vmstat output.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD